In cooled systems, including automobiles it is desirable to operate the system within a temperature range. A flow of coolant is typically used to remove heat from heat producing components in a system and transport it to a heat exchanger where it can directly or indirectly be removed from the system. For example, in an automobile the heat exchanger is in the form of a radiator, which is typically a liquid to air heat exchanger.
In many instances, it is desirable to allow the coolant temperature to first rise to a given temperature or temperature range to facilitate elevated temperature operation of the system. In this operating mode, the heat exchanger is typically not utilized with the coolant flow diverted around, or bypassing, the heat exchanger by means of a flow control device such as a conventional wax pellet driven thermostat or a flow control valve.
As the desired operating temperature range of the system is reached, heat must then be rejected (removed) from the coolant to maintain the operating temperature within the desired operating temperature range. The transition between heating and cooling of the coolant within the coolant circuit is typically accomplished by allowing some portion of the coolant to be diverted through the heat exchanger by utilizing a flow control device. The temperature of the coolant can then be maintained by blending some portion of the diverted cooled coolant with a portion which has not been cooled.
One shortcoming with the above method of maintaining an operating temperature range of a system using a bypass circuit is the occurrence of an excessive quantity of cold coolant, also referred to as a cold slug, which is released from the heat exchanger into the system when the flow control device operates to divert a portion of the coolant to the heat exchanger. The cold slug can cause excessive coolant temperature differences within the coolant circuit and therefore across the various system components within the coolant circuit, thereby leading to degraded system performance and/or reduced component life.
Thus, there is a need for improved methods to control a flow of coolant in order to avoid or control unwanted cold coolant flows within a cooled system to prevent undesired temperature differences across system components comprising the cooled system.
Therefore it is an object of the invention to provide an improved method to control a flow of coolant in order to avoid or control unwanted cold coolant flows within a cooled system to prevent undesired temperature differences across system components comprising the cooled system.